1. Field of the Invention
The present invention relates to slider needles for use with warp knitting machines, and in particular, to a minimum friction slider needle for use therewith.
2. Description of the Prior Art
Conventional warp slider needles utilized with warp knitting machines must be replaced at relatively frequent intervals since they become worn out by the friction created between the slider portion of the needle and shank portions thereof. As is well known the slider portion of the needle comes into contact with the hooked or curved portion of the shank when the needle is closed and has additional pressure exerted thereon by the threads as each stitch is knocked off the needle. Many attempts have been made over the years to reduce the amount of friction losses and heat generated by these needles and the sharpening of the hook portion and tip of the slider portion as they continually brush against each other in operation.
An early attempt to overcome this disadvantage is shown in German Pat. No. 1,760,140 which discloses a slider needle wherein the slider portion thereof does not come into contact with any portion of the groove provided in the needle shank during its backwards and forwards motion (opening and closing of the needle mouth). It is to be noted that in such a machine the free end of the slider portion is under load during the knocking over of the stitch because of the tension on the stitch threads. Since there is play between the lower end of the slider portion and the groove in the shank the slider portion will be obliged to support itself or come into contact with the hooked portion of the shank. Generally, the knockover steps overlap in time with the end of the closing of the needle mouth by the slider portion and the effect of stitch tension causes the slider portion to come into intimate contact with the hook portion of the shank. The effects of friction therebetween eventually leads to a sharpening of both the end of the slider portion and the hooked portion of the needle shank which in turn may cause the cutting of threads passing therebetween.
Another slider needle for use with warp knitting machines is shown in U.S. Pat. No. 3,229,485 which discloses a slider needle with a section cut out of the lower side of the slider portion. With this type of arrangement the slider portion, in its closed position, covers the hooked portion of the needle shank with the free end of the slider portion. With this modification the lower edge of the slider portion slides along its whole length and during its forward and backward movement in the groove coming into contact therewith. Moreover, in the closing position (where the mouth of the hook is closed by the slider portion) the lower edge of the slider portion is supported in the groove at the end thereof proximate the hooked portion of the shank so that forces acting upon the slider portion are transmitted to the hooked portion of the needle in a limited manner. However, during the sliding movement (opening and closing of the needle mouth) friction occurs in the groove and thus grinding will occur therein.